Because fire does not propagate well among saltbush, and because it thrives in a dry, arid climate, the case supporting two of the three potential causes for extinction was weakened.

Evidence suggests therefore that the P. goliah was hunted to extinction.

However, it is just one of many species whose disappearance fuels the debate, and there is much more work to be done before it can be considered a definitive proof.

"I'm a little hesitant to make a big conclusion," said co-author of the study, Larisa DeSantis of the University of Florida.

"What's really exciting is that this is one of the first instances where we've been able to use both isotopes and the microwear method to identify this very unique diet," she told BBC News.

Dr DeSantis said that she was pursuing a similar analysis of other megafauna fossils in other regions of Australia.

"This study neatly ties up several loose threads in the long-running extinction debate," said Richard Roberts of the University of Wollongong in Australia.

"By independently reaching the same conclusion for two very different environments - the mountainous rainforests of Tasmania and the dry rangelands of inland Australia - the mystery is no longer whether humans were ultimately responsible for the disappearance of the giant marsupials, but how they did it."

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